1. Field of the Invention
This invention pertains to the field of bio-affecting compositions; more specifically, it pertains to novel carboxylic acid esters which are pyrethroid insecticides, to insecticidal and acaricidal compositions containing the novel esters, and to the use of the compositions for controlling insects and acarids.
2. Description of the Prior Art
Pyrethrins have long been of interest as insecticides. Ever since it was discovered that pyrethrins are organic esters, various synthetic modifications have been made in the carboxylic acid and in the alcohol moieties on either side of the ester linkage. Many of the synthetic pyrethroids are more effective than the natural pyrethrins, and recent modifications have overcome a chronic pyrethrin problem -- instability to air and light.
The carboxylic acid moiety in the aforesaid esters is often a 2,2-dimethylcyclopropane-1-carboxylic acid with various substituents in the 3-position. A class of pyrethroids of current commercial interest contains the 2,2-dihaloethenyl group in the 3-position; for example, pyrethroids containing the 3-(2,2-dichloroethenyl)-and 3-(2,2-dibromoethenyl)-2,2-dimethylcyclopropanecarboxylic acid units are disclosed in Elliott, et al., U.S. Pat. No. 4,024,163.
Many variations in the alcohol moiety of the aforesaid esters have been disclosed also. The alcohols appearing in the most active pyrethroids of current commercial interest are well-known in the prior art and are described by the structural formula ##STR1## wherein R.sup.1 is a hydrogen atom, an alkynyl group, a methyl, or a cyano group; and R.sup.2 is a phenoxy group, a benzyl group, or a phenylthio group. Representative alcohols are 3-phenoxybenzyl alcohol and .alpha.-cyano-3-phenoxybenzyl alcohol.
According to M. Elliott, Bull. Wld. Hlth. Org., 44, 315 (1970), it is "essential for powerful pyrethrin-like activity" that the alcohol moiety, represented by HO[C-D-E-F], contain certain structural units. It is necessary that the unit C be a tetrahedral carbon atom chemically bonded, not only to the alcoholic oxygen atom O, but to unit D, the remainder of a cyclopentenolone ring, a benzene or furan ring, or C.tbd.C, so that "the carbon atoms in C, D, and E are coplanar." "The unit E is --CH.sub.2 --, --O--, or --CO--, or a sterically equivalent link, such that an unsaturated centre F (an olefinic or acetylenic bond, a conjugated system of double bonds, or an aromatic ring) can adopt a position skew to the direction defined by C, D, and E." The alcohol moieties in the most active of the pyrethroid esters of current commercial interest all contain a linking unit E, for example, --O-- in the representative alcohols named above.